The present invention relates to a material containing microaggregates of metals, organometallic compounds or inorganic compounds more particularly usable in heterogeneous catalysis and to its production process.
More specifically, the invention relates to the production of materials containing microaggregates having near-molecular dimensions and which are distributed in the material so as to form an organized structure and which consequently has novel properties and in particular a high reactivity.
For some years, attempts have been made to reduce the size of the aggregates of mineral or organometallic compounds used as the catalyst in heterogeneous catalysis because this makes it possible to increase the efficiency of the reactions, due to the increase in the available interface. In order to obtain mineral or organometallic compounds in the form of microaggregates, processes have been developed using matrixes preventing the diffusion and consequently the aggregation of compounds.
Among these processes, a process using an inert gas matrix is known consisting of mixing a metal vapor with an inert gas, then cooling the mixture to a very low temperature to obtain a solid matrix of the inert gas in which the metal is included in the form of atoms or microaggregates (cf J. Chem. Phys, 70,12,15.6.79, pp. 5683-5691).
Thus, this process makes it possible to obtain microaggregates having a size of at the most 100 .ANG., but these microaggregates are not stable as soon as the solid matrix is eliminated by raising the temperature.
Another process is known, which uses ionizing radiation to ionize a solvent containing in solution a metal salt, so as to bring about the in situ reaction of the solvated electrons obtained by ionization with the molecules of the metal salt. In this process, the subsequent aggregation of the metal particles is prevented by dispersing a soluble polymer in the solution and this prevents the diffusion of the species. It is also possible to produce platinum, iridium, rhodium, ruthenium and copper catalysts with an average particle size diameter of approximately 10 .ANG. (cf Nouveau Journal de Chimie, Vol. 6, No. 11, 1982, pp. 507-509). However, this process does not make it possible to accurately check the size of the microaggregates formed.